Recently, various wireless communication technologies have been developed, commercialized, and widely used in homes and offices, such as wireless local area network (LAN) communication based on the Institute of Electric and Electronic Engineers (IEEE) 802.11 standards and wireless personal area network (PAN) based on the wireless universal serial bus (USB) standards.
In order to connect a peripheral device to another device such as a personal computer using wireless PAN, a wireless PAN device such as a wireless board or a wireless card based on USB needs to be implemented. The wireless PAN device is provided with two or more antennas, and selects an antenna for communication that has the highest signal intensity level. This diversity control method used by the wireless PAN device is widely used in the field of portable and wireless communications such as wireless LAN and mobile phone devices. For example, as described in Japanese Patent Application Publication Nos. H08-84104, 2007-143090, and H11-298384, in the diversity control method, one antenna or a directional pattern of antenna is selected for data reception based on information regarding the strength of a received signal. For data transmission, the antenna or the directional pattern that has been previously selected for data reception is usually used.
When there are only two devices that communicate with each other, the antenna or the directional pattern that has been selected for data reception can be used for data transmission because a counterpart device is the same. However, when there are more than two devices on a wireless network, the antenna or the directional pattern that has been previously selected for data reception may not always be the most desirable one for a counterpart device as the counterpart device may change over time.
To illustrate this drawback, an example case in which two of three communication devices A, B, and C communicate with each other at an unfixed time is explained referring to FIGS. 11A and 11B. FIG. 11A illustrates a network configuration of the wireless communication devices A, B, and C. FIG. 11B is a timing chart illustrating communication condition of the wireless communication device A. As illustrated in FIGS. 11A and 11B, the wireless communication device A, which is provided with two antennas 1 and 2, selects one of the antennas 1 and 2 for communication with the wireless communication device B or C.
More specifically, referring to FIG. 11B, at the time of receiving data from the wireless communication device B, the wireless communication device A selects the antenna 1. At the time of receiving data from the wireless communication device C, the wireless communication device A selects the antenna 2. If the wireless communication device A is to transmit data to the wireless communication device B after receiving data from the wireless communication device C, the wireless communication device A continues to use the antenna 1 that has been selected for the wireless communication C, which is not suitable for communication with the wireless communication device B.